A typical sulfonic acid group-containing ether compound comprising an unsaturated double bond, a sulfonic acid (salt) group, and an ether bond is 3-allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt (hereinafter, also referred to as “HAPS”). A known method of producing HAPS comprises the steps of: reacting 1 mol of allyl alcohol with 1 mol of epichlorohydrin at 100° C. for four hours; adding 1 mol of sodium sulfite dissolved in water thereto; and reacting the mixture at 90° C. for five hours (Non-Patent Document 1). Each of Patent Documents 1 and 2 discloses that HAPS is obtainable by reacting allyl glycidyl ether with sodium bisulfite added thereto. Additionally, a polymer comprising sodium acrylate and a sulfonic acid group-containing ether compound such as HAPS is known to be favorably used in a scale inhibitor, a corrosion inhibitor, and the like (see Patent Document 3, for example).